1. Field Of The Invention
The present invention relates to a light shielding screen structure. More particularly the present invention is concerned with a light shielding screen structure having not only a high mechanical strength but also excellent optical properties, which is useful for adjusting the angles of the light rays emitted from various indicators such as indicators for instruments mounted on an instrument panel of an automobile and from image-indicating devices such as the CRT (cathode-ray tube) of a television receiver and for shielding extraneous light rays incident on the indicators or image-indicating devices, thereby preventing the deterioration of an image projected.
2. Discussion Of Related Art
Various light shielding screens have heretofore been proposed. For example, Japanese Patent Application Publication No. 55-7562/1980 and U.S. Pat. No. 2,053,173 disclose a light shielding screen which is produced by a process which comprises putting transparent plastic layers and light shielding plastic layers one upon another to form a block consisting of laminated layers and slicing the resulting block perpendicularly relative to the laminated layers.
However, in the above-mentioned conventional light shielding screen, it is difficult to precisely control the width and the thickness of the transparent layer and the light shielding layer, since in slicing the block to form a light shielding screen the transparent layer and the light shielding layer undergo deformation. Further, the process necessarily involves the step of smoothing the surface exposed by slicing. Therefore, such a light shielding screen cannot be stably produced.
On the other hand, a light shielding screen having a fine structure produced from a photocurable resin composition has been proposed in Japanese Patent Application Laid-Open Specification No. 55-139250/1980. However, in the light shielding screen disclosed in the above-mentioned patent application laid-open specification, the fine partition walls are exposed. Therefore, the light shielding screen has disadvantages in that when it is actually used for various applications, there is the disadvantage that the exposed fine structure suffers physical damage upon contact with other objects, and that foreign matter such as dust etc. may accumulate in the spaces between the partition walls, thereby decreasing the light transmission.
In order to obviate the above-mentioned disadvantages, Japanese Patent Application Laid-Open Specification Nos. 57-89701, 57-165802, 58-215880 and 60-125880 and U.S. Pat. No. 4,688,156 have proposed to fill the spaces between the partition walls with a transparent resin or attach a transparent sheet to the ends of the partition walls by means of an adhesive or a double-coated adhesive tape so as to cover up the fine partition wall structure. However, in the case where the spaces are filled with a transparent resin, it is difficult to fill up the spaces between the partition walls with the transparent resin without causing bubbles to form therein. On the other hand, in the case of attaching a transparent sheet by means of an adhesive or a double-coated adhesive tape, if the amount of the adhesive used is not enough, the bonding strength between the transparent sheet and the ends of the partition walls is too low, whereas if the amount of the adhesive is in excess, the adhesive is likely to enter the spaces between the partition walls to such a degree that transmitted light rays are scattered, resulting in a decrease in light transmission. Thus, heretofore there has not been realized a light shielding screen structure satisfying both the requirements of satisfactory bond strength and excellent optical properties.
Japanese Utility Patent Application Laid-Open Specification No. 62-9201 discloses a light shielding screen structure comprising a first light transmissible substrate having a light shielding layer thereon, and a second light transmissible substrate connected to the first light transmissible substrate through the light shielding layer. The light shielding layer comprises at least one light shielding screen portion and a light non-transmissible retaining portion which includes the entire outermost peripheral area of the light shielding layer. The second light transmissible substrate is attached to the light shielding layer at only its light non-transmissible retaining portion by means of a double-coated adhesive tape. However, in preparing this light shielding screen structure, since it is necessary to provide an adhesive tape having a shape corresponding to the shape of the light shielding screen portion, the types of light shielding screen structures which may be used are limited. Further, this type of light shielding screen structure is also disadvantageous in that since there is no bonding between the light shielding screen portion of the light shielding layer and the second light transmissible substrate, when it is intended to produce a light shielding screen structure in which the light shielding screen portion has a large area relative to the light non-transmissible retaining portion, the bonding strength between the light shielding layer and the second light transmissible substrate becomes too weak, and there cannot be obtained a light shielding screen structure having a sufficient mechanical strength as a whole.